The present invention relates generally to the field of materials melting and melting furnaces, and more particularly to materials melting by combusting ash-containing fuels for supplying heat for the melting process.
Gaseous and liquid fuels are commonly used for supplying heat to melting furnaces. Gaseous or liquid fuels are introduced into a melting furnace along with an oxidant, which may be air, oxygen-enriched air, and/or industrial oxygen, to form combustion flames overlaying the melt and/or charge. The use of solid, ash-containing fuels in melting furnaces is unusual because of the potential for the ash component to introduce defects into the molten product and the potential for the ash component to promote degradation of the furnace refractory.
Prior art for supplying heat to melting furnaces using solid fuels has taught using low ash fuel, using different furnace refractory, modifying the solid fuel to remove ash before burning the solid fuel, and operating the furnace so as to pneumatically convey the ash particles out of the melter.
U.S. Patent Application 2006/0150677 by Kobayashi for reducing corrosion and particulate emission in glassmelting furnaces states that fuels with low ash contents are preferred to lessen the risk that ash in the fuel would mix into the glassmelt and influence the glass quality as well as to lessen the risk of refractory corrosion by ash deposition. Coal and petroleum coke typically have ash contents of 5-20% and 0.1-1% respectively by weight. Thus, petroleum coke is a preferred fuel of the process of Kobayashi.
U.S. Pat. No. 6,789,396 to Olin-Nunez et al. for a method and system for feeding and burning a pulverized fuel in a glass melting furnace, and burner for use in the same, states as an object of the invention to provide a method and system for feeding and burning a pulverized fuel in a glass melting furnace, which uses special refractories for the construction of the chambers of the glass melting furnace with the object of diminishing the erosive and abrasive effects produced by the burning of said pulverized fuel, especially by the effects produced by the V2O5.
U.S. Pat. No. 4,055,400, to Stambaugh et al., U.S. Pat. No. 5,312,462 to Nowak, U.S. Pat. No. 4,741,741 to Salem et al. disclose methods for reducing the ash content of coal.
U.S. Pat. No. 4,006,003 to Daiga for a process for melting glass states that by maintaining a sufficient velocity of the flow residual ash from the burning of the coal, the residual ash can be maintained in suspension in the gaseous flow and the ash thereby pneumatically conveyed from the glass melter out of appropriate ports therein without allowing the ash to be brought into contact with the molten glass or any batch ingredients carried by the surface thereof. In this manner by adjusting the velocity of the gaseous flow above the surface of the glass substantially all of the residual ash can be removed without allowing it to come into contact with the molten pool beneath it.
It would be desirable to use ash-containing fuel without introducing unacceptable defects caused by ash.
It would be desirable to use ash-containing fuel without causing unacceptable furnace refractory degradation.